DE202015000820U1 - Scattered light smoke detector with two two-color LEDs and a common photosensor or with a two-color LED and with two photosensors each in a forward and backward scattering light arrangement - Google Patents

Abstract

A scattered-light smoke detector with a detection unit (10) operating according to the scattered-light principle, with first and second light-emitting diodes (1V, 1R) for irradiating particles to be detected and with a common photosensor (2) which is spectrally sensitive, both light-emitting diodes (1V, 1R) in each case a transmission axis (SA) and the photosensor (2) have a reception axis (EA), wherein both light-emitting diodes (1V, 1R) and the photosensor (2) are arranged and aligned with each other such that all three axes (SA, EA) in one common plane (W) lie, wherein the first light emitting diode (1V) with the photosensor (2) at a forward scattering angle (αV) and the second light emitting diode (1R) with the photosensor (2) at a backward scattering angle (αR) is arranged, characterized in that both light-emitting diodes (1V, 1R) each have a first and a second LED chip (3, 4) for emitting a respective first and second light beam (BL, RO) with light in a first and a second light beam of different second wavelength range.

Description

The invention relates to a scattered light smoke detector with a working according to the scattered light principle detection unit. The detection unit has a first and second light emitting diode for irradiating particles to be detected and a spectrally sensitive common photosensor. The two light-emitting diodes each have a transmitting axis and the photosensor has a receiving axis. Both LEDs and the photosensor are arranged and aligned with each other such that all three axes lie in a common plane. The first light-emitting diode is arranged with the photosensor at a forward scattering angle and the second light-emitting diode with the photosensor at a backward spread angle.

The invention relates to a (further) scattered light smoke detector with a detection unit operating according to the scattered light principle. The latter has a (single) LED for irradiating particles to be detected as well as a spectrally sensitive first and second photosensor. The two photosensors each have a reception axis and the light emitting diode a transmission axis. Both photosensors and the light-emitting diode are arranged and aligned with each other such that all three axes lie in a common plane. The first photosensor is arranged with the light emitting diode at a forward scattering angle and the second photosensor with the light emitting diode at a backward spread angle.

Such smoke detectors are also referred to as fire detectors. They typically have a detector housing with at least one smoke inlet opening and a detection unit for smoke detection accommodated in the detector housing. The detection unit preferably comprises an ambient light shielded, but for smoke to be detected optical measuring chamber. The latter usually has a plurality of ambient light shielding fins and is therefore also referred to as a labyrinth.

With the respective light emitting diode and the respective photosensor a control unit is connected as part of the smoke detector. The control unit is set up to output a warning message and / or an alarm message if a respective minimum concentration value of smoke can be detected.

From the prior art, such as. B. from the EP 0 877 345 A2 or from the WO 2005/043479 A1 Furthermore, smoke detectors are known which use two light-emitting diodes of different colors and a photosensor in one or two stray light arrangements. For the emission of red or infrared light, the use of a red-emitting LED or an infrared LED, for the emission of blue or violet light, the use of a blue- or violet-illuminated LED is known. By suitable evaluation of the received from the photosensor each colored scattered light, such. B. by ratio formation, then an evaluation of the particle size of the detected smoke particles is possible. By suitable evaluation of the determined particle sizes is z. As a distinction of smoke, dust and water vapor possible. The output of a possible false alarm is thereby avoided.

From the EP 1 408 469 A2 Furthermore, a scattered light fire detector is known which has two monochrome LEDs and two photoreceivers. The detector comprises a measuring chamber communicating with the ambient air, which limits a measuring volume into which an infrared-radiating and a blue-emitting LED radiate from different directions. The radiation scattered by the particles in the measuring volume is measured and evaluated photoelectrically.

It is known from the prior art, the use of two juxtaposed monochrome LEDs whose emitted light z. B. is brought together on a common optical axis via a Y-shaped optical collection element or by means of two merged optical fibers.

The considered smoke detectors are typically designed for operation on a detector line with a plurality of further connected smoke detectors or for battery-assisted stand-alone operation.

From the still unpublished European Patent Application 14155048.3 the applicant is the use of a single light emitting diode with two juxtaposed LED chips with different colors known. The first chip preferably emits red or infrared light. The second chip preferably emits blue or ultraviolet light.

Based on the above-mentioned prior art, it is an object of the invention to provide a smoke detector with an improved detection unit.

The object is achieved with the objects of the main claim 1 and 2. Advantageous embodiments of the present invention are indicated in the dependent claims.

The two main claims are based on the common idea that even with only three one-piece optoelectronic components in a forward and backward scattering light arrangement a reliable distinction between smoke, dust and water vapor in the smoke detection is possible.

According to the main claim 1, the two light-emitting diodes according to the invention each have a first and second LED chip for emitting a respective first and second light beam with light in a first and in a different second wavelength range.

According to the main claim 2, the light-emitting diode on a first and second LED chip for emitting a first and second light beam with light in a first and in a different second wavelength range.

The two-color light-emitting diode or both two-color light-emitting diodes is in each case an integral or one-piece optoelectronic component, in other words in each case one structural unit. Preferably, such a two-color light-emitting diode is a light-emitting diode with a transparent (standard) housing with a diameter of 3 mm or 5 mm. Such 3 mm or 5 mm LEDs are known to be sold "off the shelf" as a mass consumer product.

Depending on the configuration of the detection unit according to the invention, both two-color light emitting diodes or both photosensors are preferably identical components.

Alternatively, instead of one of the two two-color LEDs a monochrome LED, such. B. with only a first or second LED chip used. In this case, this LED is an IR LED, a red LED, a red / orange LED, a blue green, green, blue or ultraviolet LED.

The particular advantage is that in comparison to the detection unit according to the EP 1 408 469 A2 instead of four (one-piece) optoelectronic components only three (one-piece) optoelectronic components are needed.

In addition to the saving of a component, the outlay for the calibration of the optical path in the detection unit is advantageously reduced. Typically, the relative deviations in alignment and placement relative to one another during the assembly of two separate light-emitting diodes require a complex calibration.

Another advantage is that eliminates the optically scattered disturbance variable by the now possible elimination of the fourth component. At the location of the otherwise fourth components further light-absorbing or light-deflecting components can be used as light trap in the detection unit. As a result, the metrological disturbing fundamental impulse is reduced considerably.

The two LED chips are preferably designed as area radiators. By "surface radiator" is meant here that the light is emitted from a flat surface with a Lambertian light distribution. The area radiators can thus also be referred to as Lambert radiators. Alternatively, the LED chips may be formed as edge radiators, in which case the main emission direction of the respective edge radiator is parallel to the optical transmission axis of the light-emitting diode.

The first LED chip preferably emits light in the cyan, blue, violet or ultraviolet region, and the second LED chip emits light in the red / orange, red or infrared region.

The LED chips usually come from a wafer with a large number of LED chips produced in an optoelectronic semiconductor process. Such a wafer is decomposed by mechanical separation processes, in particular by sawing or breaking, in the plurality of LED chips. Such a "naked" and fully functional component is also referred to as "the". It therefore has a typically square or rectangular shape.

According to a preferred embodiment, the ratio of the optically active surface of the respective first LED chip to the optically active surface of the respective second LED chip in the respective light emitting diode in a range of 1.3 to 12, in particular in a range of 2.5 to 6.5.

By "optically active" is meant the parts of the surface of the LED chips that emit light when energized. Areas for contacting the LED chips on the surface, the z. B. are intended for contacting a bonding wire, thus not belong.

As a result, an adaptation of the respectively spectrally different efficiency in the generation of light in the first and in the second wavelength range is advantageously possible via the area ratio. Typically, the generation of blue or violet light is about 10 times worse than the generation of red or infrared light. For the generation of blue light with a wavelength of 470 nm (LED type SFH4570 from OSRAM) approximately 11 times the optically active surface is required for an equal irradiance as for the generation of infrared light with a wavelength of 940 nm ( LED type SFH4550 from OSRAM).

In addition, the significantly poorer spectral sensitivity of blue light in silicon PIN photodiodes, which are commonly used as photosensors. Thus, assuming the exemplary OSRAM LEDs described above, the detection of the blue light by a factor of 1.7 is worse than the detection of the infrared light (see 5 ). For the entire electrical-optical-electrical efficiency chain results in total even a factor of about 19 = 11 × 1.7.

Consequently, the optically active surface of the "blue illuminated" LED chip can be dimensioned so that a qualitatively sufficient photosensor signal for reliable smoke detection is ensured. In contrast, because of the significantly better electrical-optical-electrical efficiency of the "red" component, the surface of the "red" LED chip for generating the red or infrared light can be reduced to a fraction. This advantageously reduces the electrical power requirement and the cost of such a two-color LED.

In accordance with a further embodiment, the respective light-emitting diode has an LED chip carrier arranged orthogonally to its transmission axis. The respective two LED chips are arranged side by side on the LED chip carrier. The respective light-emitting diode is aligned so rotated about its transmission axis to the photosensor that runs through both LED chips respective chip axis orthogonal and / or parallel to the common plane.

In the case of a single two-color LED and two photosensors, their chip axis may be orthogonal or parallel to the common plane. In the orthogonal case, both light beams emitted by the LED chips can then advantageously be detected under the same scattered light angle. Thus, the two photosensor in metrological terms are better comparable. In the parallel case, and in particular when the light beam emitted by the second LED chip is directed more towards the photosensor than the first light beam, the worse light component with regard to the efficiency chain is clearly preferred.

In the case of two two-color LED with common photosensor four options for the orthogonal and / or parallel alignment of the two chip axes are possible in total.

Preferably, the respective two LED chips are arranged side by side in such a way that their respective geometric center is at the same distance from the transmission axis.

As a result, the respective emission maximum of the two LED chips is symmetrical to the transmission axis. The geometric center is z. B. in the case of LED chips with square or rectangular shape at the intersection of two surface diagonals.

According to a further embodiment, the respective first LED chip is designed to emit light in the wavelength range from 350 nm to 500 nm. The respective second LED chip is designed to emit light in the wavelength range from 665 nm to 1000 nm. In this case, the larger the distance between the two wavelength ranges from one another, the more precisely can the smoke particle size be determined. In particular, the first LED chip for emitting light having a wavelength of 460 nm is ± 40 nm or 390 nm ± 40 nm and the second LED chip for emitting light having a wavelength of 940 nm ± 40 nm or 860 nm ± 40 nm formed.

According to one embodiment, the respective light-emitting diode on a housing made of a particular transparent plastic. The housing forms an optical lens in a region between the light exit from the respective two LED chips and the light exit on the outside of the housing. By "transparent" is meant here that the plastic or glass housing is transparent at least for the light emitted by the first and second LED chip emitted light.

According to another embodiment, the respective light-emitting diode and / or the respective photosensor is an SMD component or a component for through-hole mounting. Such a two-color SMD LED also includes a transparent plastic or glass housing. As an SMD component, it is designed for direct surface mounting on a circuit carrier. The SMD LED as well as the light emitting diode for through-hole mounting can also be a light guide or a mirror optically connected downstream, which the emitted light beam z. B. by 90 °.

The two LED chips are aligned orthogonally to the transmission axis, ie to the main optical axis of the light emitting diode on the chip carrier. In other words, the surface normal of the particular planar chip carrier runs parallel to the transmission axis. The two LED chips are arranged side by side on the LED chip carrier and consequently also flat on the LED chip carrier. Their respective surface normal also run parallel to the main optical axis of the light emitting diode.

The LED chip carrier does not necessarily have to be designed flush. It can also have two slightly mutually inclined partial surfaces in the sense of a notch, each receiving an LED chip. As a result, the two emitted light beams are aligned with each other (see 8th ). The chip carrier may also have two planar faces with the same orientation, but separated by a step. The stepping can be selected so that with different component thickness of the two LED chips, the optically active surfaces lie in a common plane (see 9 ).

According to one embodiment, the smoke detector has an electronic control unit connected to the respective light-emitting diode and to the respective photosensor. The control unit is set up to issue a warning message and / or an alarm message if a minimum concentration value of smoke can be detected. The control unit is preferably a microcontroller. It is set up, depending on the configuration of the detection unit, either to electrically actuate the two LED chips of the single two-color LED for emitting the respective light and to synchronously detect and evaluate the respective electrical signal from both photosensors. Or the control unit is configured to electrically control both LED chips of the two two-color LEDs for emitting the respective light and synchronized to detect and evaluate the electrical signal from the common photosensor. By difference formation or ratio formation from the two respective, the "color" associated received signal amplitudes of the photosensor or the two photosensors and depending on the respective scattering angle then a determination of the particle size and the particle type such as smoke, dust or steam is possible. By comparing preferably the "blue" signal with a respective minimum concentration value, a warning message and / or an alarm message can be output. The respective processing steps for the temporal control of the two LED chips as well as the synchronized detection and evaluation of the respective photosensor signal can be realized by suitable, executable on the microcontroller program steps.

According to another embodiment, the respective photosensor is a semiconductor photodiode, in particular a silicon PIN photodiode. It is preferably a silicon PIN photodiode with improved blue sensitivity.

Furthermore, according to a further embodiment, both LED chips of the respective light-emitting diode can be alternately pulsed or simultaneously pulsed by the electronic control unit. In the first case, only one photosensor is required. In the second case, two photosensors may be required for the particular scattered light to be detected.

The control unit can also be set up to control the respective first LED chip with its specified nominal current. The control unit can furthermore be set up to control the respective second LED chip with a reduction factor which can be defined in comparison with its specified nominal current.

By "specified rated current" is meant here the nominal current value specified by the light-emitting diode manufacturer typically in a data sheet. This advantageously makes it possible to reduce the electrical power required for the operation of the second LED chip. The reason for this is a production and assembly-related minimum chip size for the second LED chip, ie for the red-glowing LED chip. By the reduction factor, which is typically in the range between 2 to 4, so to speak an "electronic reduction" of the chip area of the second LED chip is effected. In addition, a calibration of the drive for the first and second LED chip is advantageously possible via this reduction factor. The power reduction and thus the power reduction can z. B. by means of a pulse width modulated control of the second LED chip. The reduction factor in the range of 2 to 4 corresponds to the duty cycle of the pulse width modulation. The drive frequency is preferably in the range of 100 kHz to 10 MHz.

Preferably, the reduction factor is determined by the different spectral sensitivity of the photosensor for scattered light to be detected in the first and second wavelength range.

In the case of a detection unit having two bicolor LEDs and a common photosensor in which the first light emitting diode with the photosensor is disposed at a forward scattering angle and the second light emitting diode with the photosensor at a backward scattering angle, the forward scattering angle is in a range of 20 ° to 90 ° , in particular in a range of 30 ° to 70 °. The backward angle is in one Range of more than 90 ° to 160 °, in particular in a range of 110 ° to 150 °. In particular, the forward scatter angle is 60 ° and the backward spread angle is 120 °.

In the case of a detection unit having two photosensors and a single two-color light emitting diode in which the first photosensor with this light emitting diode is disposed at a forward scattering angle and the second photosensor with this light emitting diode is disposed at a backward spread angle, the forward scattering angle is in a range of 20 ° to 90 ° , in particular in a range of 30 ° to 70 °. The backward angle is in a range of more than 90 ° to 160 °, in particular in a range of 110 ° to 150 °. In particular, the forward scatter angle is 60 ° and the backward spread angle is 120 °.

The invention and advantageous embodiments of the present invention will be explained using the example of the following figures. Showing:

1 an exemplary according to the scattered light principle working first embodiment of a detection unit for a smoke detector with two bi-color LEDs and with a photoreceiver according to the invention,

2 a second embodiment with two bicoloured LEDs and with a photoreceiver according to the invention,

3 a third embodiment with two photoreceivers and with a single common two-color light-emitting diode according to the invention,

4 A fourth embodiment with two photoreceivers and with a single common two-color light-emitting diode according to the invention,

5 a plan view of a two-color LED with two LED chips in a first embodiment,

6 a plan view of a two-color LED with two LED chips in a second embodiment,

7 - 9 various designs of an LED chip carrier with two recorded LED chips,

10 an example of a scattered light smoke detector according to the invention with a smoke-permeable, but with respect to ambient light shielded detection unit arranged inside, and

11 an example of the specific spectral sensitivity of a silicon PIN photodiode with increased sensitivity to blue.

1 shows an exemplary according to the scattered light principle working first embodiment of a detection unit 10 for a smoke detector 100 with two bi-color LEDs 1V . 1R and with a photoreceptor 2 according to the invention.

For reasons of clarity, one is the detection unit 10 surrounding smoke detector housing not shown (see 11 ). Likewise, the representation of a typically recorded in the smoke detector housing circuit board with control unit and the representation of smoke inlet openings in the smoke detector housing has been omitted.

The detection unit 10 has an optical measuring chamber with a plurality of ambient light shielding fins 11 on. The slats 11 are arranged in the circumferential direction so that substantially all the direct light from the two LEDs 1V . 1R and stray light in the interstices of the slats 11 is steered. The incident light "caught" then there under repeated attenuating back and forth reflection in the sense of a light trap.

Inside the detection unit 10 are according to the invention, two construction or type identical two-color LEDs 1V . 1R and a spectrally sensitive common photosensor 2 shown. Both LEDs 1V . 1R each have a transmission axis SA and the photosensor 2 a reception axis EA. All three optical axes SA, EA lie in a common plane W.

All three optoelectronic components 1V . 1R . 2 also have screens 12 so that no direct emitted light from the LEDs 1V . 1R to the photosensor 2 arrives. Through the apertures 12 is optically constructive of the respective transmission range of the LEDs 1V . 1R as well as the reception area of the photosensor 2 established. The common intersection or the intersection volume then forms the so-called scattering volume SV for optical smoke detection. Inside the detection unit 10 can still be more apertures exist such. As a pinhole, or optical means such as lenses.

In the present example, the first light-emitting diode 1V at a forward scattering angle αV of 60 ° to the photosensor 2 arranged. The second LED 1R is at a backscatter angle αR of 120 ° to the same photosensor 2 arranged.

Structurally, the two scattering angles αV, αR are represented by the intersection of the respective transmission axis SA and the reception axis EA of the common photosensor 2 established. The two intersections are identical. In practical terms, not all optical axes SA, EA need to intersect at this one intersection. Minor angular deviations of a few degrees, in particular less than 1 °, can be disregarded in practice.

Both LEDs 1V . 1R each have a first and second LED chip 3 . 4 on. The respective first LED chip 3 is to send a first light beam BL formed with light in a first wavelength range. In the present example, the first LED chip emits 3 with electrical excitation monochromatic blue light at a wavelength of 460 nm ± 40 nm. The second LED chip 4 emits monochromatic infrared light at a wavelength of 940 nm ± 40 nm when electrically excited. The light-emitting diodes 1V . 1R have a plastic housing, which is an optical lens for light bundling of the respective light emitting diode 1V . 1R generated light in the direction of the scattering volume SV forms. The two LEDs 1V . 1R as well as the photosensor 2 correspond in their external appearance that of a typical 5 mm LED for a "through hole assembly" with a diameter of the plastic housing of 5 mm. Alternatively, this may be a 3 mm LED.

Both components 1V . 1R . 2 are typically electrically connected to a circuit carrier, which is usually outside the detection unit 10 located and adjacent to this. On the circuit board further components may be arranged such. As a microcontroller, active or passive components.

The inventive arrangement of the two two-color LEDs 1V . 1R which is at a forward scattering angle αV and at a backward scattering angle αR with the common photosensor 2 are arranged and aligned allowed in only three optical components 1V . 1R . 2 a reliable smoke detection. For metrological evaluation are thus scattered light signals with two different "colors" at two different scattering angles αV, αR available.

2 shows a second embodiment with two two-color LEDs 1V . 1R and with a photoreceptor 2 according to the invention. Compared to the previous embodiment, the two transmission axes SA of the LEDs 1V . 1R now on a common optical axis. The scattering volume SV is even identical here for both "colors" in comparison to the previous embodiment. In contrast, the respective opposite LED acts 1V . 1R like an optical scattering body, which is unfavorable for a metrological evaluation.

3 shows a third embodiment with two photoreceptors 2V . 2R and with a single common bi-color LED 1 according to the invention.

Also, this inventive arrangement of two photosensors 2V . 2R and a common two-color LED 1 which is at a forward scattering angle αV and at a backward angle αR with the respective photosensor 2V . 2R is arranged and aligned, allowed for only three optical components 2V . 2R . 1 a reliable smoke detection. For metrological evaluation, scattered light signals with two different "colors" are also available at two different scattering angles αV, αR.

4 shows a fourth embodiment with two photoreceptors 2V . 2R and with a single common bi-color LED 1 according to the invention.

Compared to the previous embodiment, the two receiving axes EA of the photosensors 2V . 2R now on a common axis. The scattering volume SV is identical here for both "colors" in comparison to the previous embodiment. In contrast, a respective opposite photo sensor acts 2V . 2R for the other as an optical scattering body, which is also unfavorable here for a metrological evaluation.

5 shows a plan view of a two-color LED 1 . 1V . 1R with two LED chips 3 . 4 in a first embodiment.

With the reference number 9 is called a plastic housing in which the LED chip carrier 6 as part of a reflector 5 with the two LED chips 3 . 4 is poured. The reflector 5 is at the same time as common connection contact 7 formed and as a middle connection contact 70 out of the case 9 led out. The middle connection contact 70 is on both sides by a first and second connection contact 71 . 72 Surrounded by the electrical connection with the two LED chips 3 . 4 proceed. The two connection contacts 71 . 72 form in the area of the LED chip carrier 6 in each case one contacting surface for contacting the two LED chips 3 . 4 with these over bonding wires 8th out.

The light-emitting diode 1 . 1V . 1R has an LED chip carrier arranged orthogonal to its transmission axis SA 6 on. The chip carrier 6 is plate-shaped and flat. In other words, the surface normal of the LED chip carrier 6 parallel to the transmission axis SA. The two LED chips 3 . 4 are also next to each other on the LED chip carrier 6 arranged. The LED shown 1 . 1V . 1R is aligned so rotated about its transmission axis SA to the photosensor that one through both LED chips 3 . 4 extending chip axis CA orthogonal to the common angle plane W runs. QA denotes a transverse axis, which is orthogonal to the chip axis CA and to the transmission axis SA.

By the "superposition" of the two LED chips 3 . 4 be the two colored scattered light signals from the perspective of the common Photosensors or from the perspective of both photosensors under a same scattered light angle received.

As the 5 further shows, the ratio of the optically active surface of the first LED chip 3 to the optically active surface of the second LED chip 4 in a range of 1.3 to 12, in particular in a range of 2.5 to 6.5. In the present example, the ratio is about 2.78 = (0.5 × 0.5 mm) ² /(0.3 × 0.3 mm) ² , wherein the side length of the two exemplary square LED chips 3 . 4 have an edge length of 0.5 mm or 0.3 mm. In addition, the two LED chips 3 . 4 already arranged side by side such that the respective geometric center of the two LED chips 3 . 4 an equal distance to the transmission axis SA of the LED 1 . 1V . 1R having. The respective geometric center is indicated by a small "x".

The edges of the two LED chips 3 . 4 are preferably aligned parallel and orthogonal to each other. In particular, the two LED chips 3 . 4 then centered, so centered to each other. This already shows the present 5 , In such a case, the chip axis CA can also be defined or defined as a straight line which passes both through the geometric center of the first LED chip 3 as well as through the middle of the second LED chip 4 runs. In the ideal case shown the 5 are the two LED chips 3 . 4 aligned with each other and on the chip carrier 6 arranged that the chip axis CA also still through the transmission axis SA of the light emitting diode 1 . 1V . 1R runs.

6 shows a plan view of a two-color LED 1 . 1V . 1R with two LED chips 3 . 4 in a second embodiment. In this case, the respective light-emitting diode 1 . 1V . 1R so turned around its transmission axis SA to the photosensor that one through both LED chips 3 . 4 extending chip axis CA parallel to the common angle plane W runs.

7 shows a flat LED chip carrier 6 with two adjacent LED chips 3 . 4 , This shows the "red" LED chip 4 compared to the "blue" LED chip 3 a larger component thickness.

The 8th and 9 show that the LED chip carrier 6 not necessary plan must be executed. In the example of 8th has the LED chip carrier 6 two slightly mutually inclined partial surfaces in the sense of a notch, which each have an LED chip 3 . 4 take up. The two faces are also flat. In the example of 9 has the LED chip carrier 6 likewise two partial surfaces. These have the same orientation in comparison to the previous embodiment. Both faces are through a step in the chip carrier 6 separated from each other. The graduation is chosen so that with different component thickness of the two LED chips 3 . 4 their optically active surfaces lie in a common plane.

10 shows an example of a scattered light smoke detector according to the invention 100 with a detector housing 13 and with an opening OF for the possible passage of smoke to be detected. The detector housing 13 is made up of a basic body 14 and from a detector cap 15 together. In the detector housing 13 is a shielded from ambient light, but permeable to smoke detection unit 10 arranged. With "shielded" here is a shield of the detection unit 10 meant to direct ambient light. With the reference number 16 is an insect repellent called against the ingress of insects. With the reference number 18 is a microcontroller called a control unit, on a circuit board as a circuit carrier 17 is arranged. The microcontroller 18 is set up to control the respective two-color LEDs, to detect a sensor signal from the respective photosensor and to metrologically evaluate the signals and to output a warning message and / or alarm message AL, if a minimum concentration value of smoke can be detected.

11 shows an example of the specific spectral sensitivity S _{Rel of} a silicon PIN photodiode 2 with increased blue sensitivity. The abscissa represents the light wavelength λ of the detected light in nanometers, the ordinate represents the specific spectral sensitivity S _Rel using the example of a silicon PIN photodiode of the type BPW34B from OSRAM in percentages. The spectral sensitivity S _Rel is normalized with a 100% value to the spectrally sensitive light wavelength at 850 nm. As the diagram shows, the spectral "blue" sensitivity is SEB of the photosensor 2 for blue light with a wavelength value Λ1 of 470 nm at 52%, about 1.7 times worse than the spectral "red" sensitivity SER of the photosensor 2 for infrared light at a wavelength value Λ2 of 940 nm with 90%.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0877345 A2 [0005]
• WO 2005/043479 A1 [0005]
• EP 1408469 A2 [0006, 0018]
• EP 14155048 [0009]

Claims (15)

Scattering light smoke detector with a detection unit operating according to the scattered light principle ( 10 ), with a first and second light emitting diode ( 1V . 1R ) for irradiating particles to be detected and with a spectrally sensitive common photosensor ( 2 ), both LEDs ( 1V . 1R ) one transmitting axis (SA) and the photosensor ( 2 ) have a reception axis (EA), wherein both light-emitting diodes ( 1V . 1R ) as well as the photosensor ( 2 ) are arranged and aligned with each other such that all three axes (SA, EA) lie in a common plane (W), wherein the first light-emitting diode ( 1V ) with the photosensor ( 2 ) at a forward scattering angle (αV) and the second LED ( 1R ) with the photosensor ( 2 ) is arranged at a backward spread angle (αR), characterized in that both light emitting diodes ( 1V . 1R ) each have a first and second LED chip ( 3 . 4 ) for emitting a respective first and second light beam (BL, RO) with light in a first and in a different second wavelength range. Scattering light smoke detector with a detection unit operating according to the scattered light principle ( 10 ), with a light-emitting diode ( 1 ) for irradiating particles to be detected and with a spectrally sensitive first and second photosensor ( 2V . 2R ), both photosensors ( 2V . 2R ) one receiving axis (EA) and the light emitting diode ( 1 ) have a transmission axis (SA), both photosensors ( 2V . 2R ) as well as the light emitting diode ( 1 ) are arranged and aligned with each other such that all three axes (EA, SA) lie in a common plane (W), wherein the first photosensor ( 2V ) with the light-emitting diode ( 1 ) at a forward scattering angle (αV) and the second photosensor ( 2R ) with the light-emitting diode ( 1 ) is arranged at a backward spread angle (αR), characterized in that the light emitting diode ( 1 ) a first and second LED chip ( 3 . 4 ) for emitting a first and second light beam (BL, RO) with light in a first and in a different second wavelength range. A scattered light smoke detector according to claim 1 or 2, wherein the ratio of the optically active surface of the respective first LED chip ( 3 ) to the optically active surface of the respective second LED chip ( 4 ) at the respective light emitting diode ( 1V . 1R . 1 ) is in a range from 1.3 to 12, in particular in a range from 2.5 to 6.5. Scattered light smoke detector according to one of the preceding claims, - wherein the respective light emitting diode ( 1V . 1R . 1 ) an LED chip carrier orthogonal to its transmission axis (SA) ( 6 ), wherein the respective two LED chips ( 3 . 4 ) side by side on the LED chip carrier ( 6 ), and - wherein the respective light-emitting diode ( 1V . 1R . 1 ) is rotated about its transmission axis (SA) to the photosensor ( 2 . 2V . 2R ), that one through both LED chips ( 3 . 4 ) extending respective chip axis (CA) is orthogonal and / or parallel to the common plane (W). Stray light smoke detector according to one of the preceding claims, wherein the respective two LED chips ( 3 . 4 ) are arranged side by side in such a way that their respective geometric center is at the same distance from the transmission axis (SA) of the respective light-emitting diode (FIG. 1V . 1R . 1 ) having. Scattered light smoke detector according to one of the preceding claims, wherein the respective first LED chip ( 3 ) is designed to emit light in the wavelength range of 350 nm to 500 nm and wherein the respective second LED chip ( 4 ) is designed to emit light in the wavelength range from 665 nm to 1000 nm. Stray light smoke detector according to claim 6, wherein the respective first LED chip ( 3 ) for emitting light having a wavelength of 460 nm ± 40 nm or 390 nm ± 40 nm and the respective second LED chip ( 4 ) is designed to emit light having a wavelength of 940 nm ± 40 nm or 860 nm ± 40 nm. Scattered light smoke detector according to one of the preceding claims, wherein the respective light emitting diode ( 1V . 1R . 1 ) a housing ( 9 ) made of a particularly transparent plastic and wherein the housing ( 9 ) in a region between the light exit from the respective two LED chips ( 3 . 4 ) and the light exit on the outside of the housing ( 9 ) an optical lens ( 14 ) trains. Scattered light smoke detector according to one of the preceding claims, wherein the respective light emitting diode ( 1V . 1R . 1 ) and / or the respective photosensor ( 2 . 2V . 2R ) is an SMD component or a device for a through hole mounting. Scattered light smoke detector according to one of the preceding claims, wherein the scattered light smoke detector with the respective light emitting diode ( 1V . 1R . 1 ) and with the respective photosensor ( 2 . 2V . 2R ), wherein the control unit is adapted to output a warning message and / or an alarm message if a minimum concentration value of smoke is detectable. Scattered light smoke detector according to one of the preceding claims, wherein the respective photosensor ( 2 . 2V . 2R ) is a semiconductor photodiode, in particular a silicon PIN photodiode. Stray light smoke detector according to one of the preceding claims, wherein the respective two LED chips ( 3 . 4 ) are pulsed alternately controlled by the electronic control unit. Scattered light smoke detector according to one of the preceding claims, wherein the respective two light-emitting diodes ( 1V . 1R ) or the respective two photosensors ( 2V . 2R ) are identical components. Scattered light smoke detector according to one of the preceding claims, wherein the forward scattering angle (αV) in a range of 20 ° to 90 °, in particular from 30 ° to 70 °, and the backward scattering angle (α) in a range of more than 90 ° to 160 °, in particular from 110 ° to 150 °. Scattered light smoke detector according to one of the preceding claims, wherein the scattered light smoke detector, a detector housing ( 13 ) with at least one opening (OF) for the possible passage of smoke to be detected and in the detector housing ( 13 ), shielded from ambient light detection unit ( 10 ) having.

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